--> Evaluation and Analysis of Frontal Structures in the Papuan Fold-and-Thrust Belt—An Integrated Approach to Refining Structural Uncertainty

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Evaluation and Analysis of Frontal Structures in the Papuan Fold-and-Thrust Belt—An Integrated Approach to Refining Structural Uncertainty

Abstract

The Papuan fold-belt forms part of the deformed northern Australasian Plate margin, which records contractional deformation from the late Miocene through to the present. The deformation styles are complex and only partially understood–there is compelling evidence for basement-involved inversion, thin-skinned detached thrusting, and complex interplays of both styles. The aim of this paper is to evaluate a selection of profiles through the frontal portion of the fold belt, from NW PNG to the Gulf of Papua, characterise them, and present a model for controls on deformation and how to recognise them on varied datasets. The concept of structural uncertainty is evaluated, with the view to improving our spatial and temporal understanding of the fold belt's evolution, and better understanding anticline formation and geometry. The frontal structures are chosen for multiple reasons. There is a more complete dataset here relative to other parts of the fold belt, consisting of well, seismic reflection, airborne and ground gravity, airborne magnetics, field geological and remotely sensed data. There is only partial evidence for multiple break-forward deformation, supported by moderately shallow back-limb rotation. Finally, there is a close spatial association between the frontal structures and commercial oil and gas accumulations. Key observations utilised in this study rely on: (1) renewed interpretations and processed products derived from seismic data; (2) a new regional airborne gravity and magnetics dataset; (3) better understanding of pre-deformed “regional” level; (4) more complete characterisation of detachment level via mechanical attributes tied with stratigraphic observations; (5) a better understanding and characterisation of pre-contractional structures including syn-rift geometries and structural embayments. A significant result of this work shows that utilisation and integration of all available datasets can reduce structural uncertainty, and hence reduce geological and hydrocarbon trap risk. The implications include better definition of potential hydrocarbon trapping configurations and increased chance of hydrocarbon accumulation success in a leading-edge structural setting.